1. Field of the Invention
The present invention relates generally to an air conditioning unit and method of controlling the same, and more particularly to an air conditioning unit and method of operating the same, which can reduce power consumption by controlling the level of power supplied to a motor of a compressor according to an operation cycle of the compressor.
2. Description of the Prior Art
Recently, as buildings have become large-sized, demand for multi-air conditioners in which an outdoor unit is connected to a plurality of indoor units has increased.
In general, the individual indoor units of such a multi-air conditioner have different required cooling capacities, and are independently operated, such that a total cooling capacity obtained by summing up the required cooling capacities of all indoor units is also varied. In order to meet the variation of the total required cooling capacity, the capacity of a compressor is adjusted according to the variation of the total required cooling capacity, and the opening ratio of an electric expansion valve situated upstream of an indoor heat exchanger or evaporator is controlled for each of the indoor units.
There are a variable-speed compressor and a pulse width modulation (PWM) compressor as a variable-capacity compressor having a capacity to be varied according to the variation of a required cooling capacity.
The PWM compressor adjusts the capacity of the compressor to correspond to a required cooling capacity by varying the capacity of the compressor in response to a duty control signal used to determine a loading operation for discharging a cooling agent and an unloading operation for not discharging the cooling agent.
Meanwhile, the PWM compressor is supplied with power regardless of whether the loading or the unloading operation is proceeded, and a motor of the compressor rotates at constant speed. Further, if the supply of power to the compressor is interrupted, the compressor motor does not rotate, and the operation of the compressor stops.
In the PWM compressor, power required for the loading operation is greater than that for the unloading operation, which is due to a fact that much power is required for compressing the cooling agent during the loading operation. Further, during the unloading operation, only minimal power for no-load operation is required, such that the unloading operation requires little power relatively to the loading operation.
However, in the conventional PWM compressor, a compressor driving circuit to drive the compressor is produced in consideration of the loading operation, that is, an operating condition of high power consumption. Accordingly, even during the unloading operation of the PWM compressor, driving power is supplied under the same condition as that of the loading operation, thus causing undesirable power consumption during the unloading operation.
The PWM compressor periodically repeats the unloading operation and the loading operation according to a required cooling capacity. Therefore, undesirable power consumption occurs inevitably whenever the PWM compressor performs the unloading operation. Consequently, there is required an improved method of controlling power (power level) according to an operation cycle of the compressor.